1. Technical Field
The present invention relates generally to a scanner motor and, more particularly, to a scanner motor which is used in an output device using optical technology, such as a laser beam printer or a scanner, so as to rotate a polygon mirror.
2. Description of the Related Art
As the market for output devices using optical technology requires miniaturization and high speed, higher performance must be provided to an actuator for driving an optical reflecting device, the important part of which is a polygon mirror.
The most important performance factor which is required recently is the flatness of the optical reflecting unit such as the polygon mirror and the rotating center of a rotating shaft when it is in operation. Further, the reduction in manufacturing cost as well as performance is important matters to be considered.
The scanner motor is the machine which is installed in a laser beam printer or the like and rotates a polygon mirror at high speed to deflect and scan optical beams emitted from a light source. In the scanner motor, the polygon mirror rotating at high speed must be mounted and secured to the scanner motor. A conventional scanner motor is schematically shown in FIG. 7.
As shown in FIG. 7, the conventional scanner motor 10 includes a polygon mirror 11 which is provided on the upper portion of the scanner motor 10, and a spring 12 which is used to couple the polygon minor 11 to the housing shaft 13. Such a conventional scanner motor is disclosed in Korean Patent Laid-Open Publication No. 2003-84148.
The scanner motor 10 rotates a housing shaft 13 with force between a stator (not shown) which is mounted to the outer circumference of a bearing holder (not shown) and is thus subjected to external power, and a rotor magnet 15 which is mounted to the inner circumference of the rotor case 14.
The housing shaft 13 mounts the polygon minor 11, and the rotor case 14 is mounted to the lower portion of the housing shaft 13.
The housing shaft 13 has a disc shape, with the polygon mirror 11 mounted to the housing shaft 13. A rotating shaft 16 is inserted into the central portion of the housing shaft 13 to be secured thereto. The spring 12 is pressed against the upper surface of the housing shaft 13, thus locking the upper portion of the polygon mirror 11.
The rotor case 14 is secured to the lower surface of the housing shaft 13 using caulking, and the rotor magnet 15 is mounted to the inner circumferential wall of the rotor case 14 in such a way as to face the stator (not shown).
The polygon mirror 11 is mounted to the housing shaft 13 of the scanner motor 10 in such a way as to be rotated, and reflects laser beams in a laser beam printer or the like. Here, at least part of the upper surface of the polygon minor 11 is pressed by the spring 12 installed to the housing shaft 13 to be secured to the housing shaft 13.
However, the scanner motor 10 constructed as described above is problematic in that the housing shaft 13, serving as the support part of the polygon minor 11 and manufactured through machining, is used to secure the flatness of the rotating shaft 16 and the polygon minor 11, and coupling force between the spring 12 and the polygon mirror 11 is low, so that the spring 12 and the polygon mirror 11 is separable from the scanner motor 10 in case there is a strong impact transmitted from the exterior.
Further, the spring 12 may be deformed by floating force of the polygon mirror 11 when the scanner motor 10 rotates at high speed. Thereby, the overall balance of the scanner motor 10 is impaired, so that it is impossible to obtain the stable driving characteristics of the scanner motor 10.
Therefore, there is an urgent need for research into a scanner motor, which is capable of preventing the dislocation of the polygon mirror 11, and of firmly retaining the polygon mirror 11, thus keeping the balance of the polygon mirror 11 stable, and reducing the manufacturing cost of parts.